1. Field of the Invention
The present invention generally relates to a control system for controlling a plurality of electronic apparatus, such as a home bus system and, more particularly, is directed to a signal transmission system.
2. Description of the Prior Art
In recent years, a home bus system has been practically used in homes. This home bus system connects various different electronic apparatus such as, for example, a personal computer, illumination control terminals, gas leakage sensor and so on by a transmission cable and provides various controls on the apparatus. In addition, the assignee of the present application has previously proposed the Multi Link System (hereinafter simply referred to as an MLS) in which audio and video informations are distributed through wires from one room of a home to each room where the information can be selectively viewed and listened to. Japanese Patent Laid-open Publication No. 2-226890 describes this previously-proposed MLS which will be described below.
Of a plurality of rooms of a house, a basement or a parlor or the like, for example, is used as a Master Room. Within this Master Room, a plurality of electronic apparatus, for example, a CD (compact disc) player, tape cassette deck, a VTR (video tape recorder) or the like, a multi-link center such as a multi-preamplifier or the like to which these electronic apparatus are connected and which controls the same are concentratedly installed. Whereas, multi-link receivers are installed in other rooms through cables in order that audio information and video information from the above-mentioned plurality of electronic apparatus can be listened to and viewed by means of remote controllers. Thus, by operating the remote controller provided in each of the multi-link receivers, it is possible for the user selectively to view and listen to desired informations in each room from various electronic apparatus connected to the multi-link center in the master room.
In the above-mentioned MLS, audio informations and video informations (AV informations) from predetermined electronic apparatus within the Master Room are assigned to independent channels at various kinds of electronic apparatus and these informations are frequency-multiplexed and transmitted to respective rooms via the single cable. However, with the increase of electronic apparatus connected to the multi-link center, many independent channels are needed and many frequency bands also are needed in order to transmit AV informations. These frequency bands must be selected so as not to overlap frequency bands of television broadcast, AM and FM radio broadcasts, police wireless communication system or the like now available on a wide variety of countries. Therefore, it is requested that information as much as possible can be transmitted by means of less number of channels and within a narrower frequency band.
However, if the number of channels is reduced, then the kind of AV informations transmitted is restricted. To remove this disadvantage, the MLS must be designed so that the same AV informations can be listened to and viewed within a plurality of rooms. At that time, if the user in one room operates the remote controller, the supply of the same AV informations to other rooms is interrupted. There is then the risk that the whole MLS system will be disturbed.